值得注意的是，独立按键的检测原理和消抖处理在51单片机中已经讲过了，这些东西都不会变。只是AVR单片机的IO口操作方式改变了。在AVR中，检测方式是：首先让将和独立按键相连接的IO口设置成输出高电平，接着将他们设置成输入模式，再然后检测这些IO口的值。电路图如下所示。

代码1：检测是哪一个按键被按下。这里不需要用到消抖动处理。

#include<iom16v.h>
#include<macros.h>
#define uint unsigned int
#define uchar unsigned char
uchar table[] = {0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80};
void keyScan();
void initSYS();
void main()
{
 	 initSYS();
	 while(1)
	 {
	  	keyScan();
	 }
}

void initSYS()
{
 	 //init the system
	 DDRB = 0xFF;
	 PORTB = 0xFF;
	 
	 DDRA = 0xFF;
	 PORTA = table[0];
}

void keyScan()
{
 	 //to check wether the key has pressed
	 uchar isPressed;
	 DDRB = 0x00;
	 isPressed = PINB;
	 if(isPressed != 0xFF)
	 {
	  	 switch(isPressed)
		 {
		     case 0x7F:
			 	  PORTA = table[1];
			 	  break;
			 case 0xBF:
			 	  PORTA = table[2];
			 	  break;
			 case 0xDF:
			 	  PORTA = table[3];
			 	  break;
			 case 0xEF:
			 	  PORTA = table[4];
			 	  break;
			 case 0xF7:
			 	  PORTA = table[5];
			 	  break;
			 case 0xFB:
			 	  PORTA = table[6];
			 	  break;
			 case 0xFD:
			 	  PORTA = table[7];
			 	  break;
			 case 0xFE:
			 	  PORTA = table[8];
			 	  break;
		 }
	 }
	 else
	 {
	  	 //PORTA = table[0];
	 }
}

#include<iom16v.h>
#include<macros.h>
#define uint unsigned int
#define uchar unsigned char
uchar table[] = {0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};
uchar num;
void init();
void delay();
void keyScan();
void main()
{
 	 init();
	 while(1)
	 {
	  	keyScan();
	 }
}

void init()
{
 	 DDRA = 0xFF;
	 PORTA = table[0];
	 
	 DDRB = 0xFF;
	 PORTB = 0xFF;
	 
	 num = 0;
}

void keyScan()
{
 	 uchar keyValue;
	 DDRB = 0x00;
	 keyValue = http://www.mamicode.com/PINB;>


AVR第8课：独立按键